Conduit plug for separating fluids



April 8, 1969 SCOTT 3,437,137

CONDUIT PLUG FOR SEPARATING FLUIDS Filed Oct. 15, 1967 INVENTOR V46 5.560T) A TTOZ/Vy April 8, 1969 L. B. SCOTT Filed 001.- 13, 1967 CONDUITPLUG FOR SEPARATING FLUIDS INVENTOR United States Patent O 3,437,137CONDUIT PLUG FOR SEPARATING FLUIDS Lyle B. Scott, South Gate, Califi,assignor to Byron Jackson Inc, Long Beach, 'Calif., a corporation ofDelaware Filed Oct. 13, 1967, Ser. No. 675,237 Int. Cl. EZlb 33/16 US.Cl. 166-453 9 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THEINVENTION Field of the invention This invention relates to pipe plugswhich may be pumped through a pipe conduit for keeping pumped fluidsseparated. More specifically, the invention is related to oil wellcementing plugs used when pumping a cement slurry down through a wellcasing to force it into the annular space between the casing and thewell bore to cement the casing in place and seal off the formationstrate.

Whenever an oil well is drilled, casing is lowered into the Well bore,which is generally filled with drilling mud. The casing must be cementedin place by pumping a predetermined amount of cement slurry down throughthe casing, out the bottom, and up into the annular space between thecasing and the Well bore, displacing the drilling mud ahead of it. Inorder to completely pump out the cement slurry from the casing,additional fluid, which may be drilling mud, is pumped behind theslurry. To avoid contamination of the cement slurry, a forward or bottomcementing plug with a frangible diaphragm and made of rubber or otherelastomeric material is inserted in the casing between the drilling mudand the slurry, and a following or top cementing plug, also of resilientmaterial, may be inserted above the cement, ahead of the pumping fluid.When the bottom plug is pumped down against an annular seat or stop nearthe lower end of the casing, differential pressure then causes itsdiaphragm to rupture, allowing the cement slurry to flow out the bottomof the casing and into the annulus. When the top plug reaches the bottomplug, a seal is effected, allowing no more flow, and the cement isallowed to set. Depending on subsequent operations required in the well,the plugs and any residual cement in the casing may then be drilled out.

Description of the prior art Heretofore, cementing plugs as commonlyused in oil well cementing operations have been of the type shown anddescribed on page 2281 of the 1966-67 (27th revision) of the CompositeCatalog of Oil Field Equipment and Services, published by World Oil, aGulf Publishing Company Publication, Post Oflice BoX 2608, Houston, Tex.77001.

The plugs have a generally cylindrical body portion, usually made ofrubber or synthetic rubber, and substantially smaller in outsidediameter than the inside of the casing, the body portion beingreinforced by a generally cylindrical metal portion, usually of aluminumso that it is drillable, and around which the rubber body is molded. Theplugs have a series of parallel, flexible lips, integral with the bodyportion, formed during the molding process, the lips being larger inoutside diameter than the bore of the casing in order to provide awiping and sealing action against the casing Wall; and the lips effect alimited amount of resilient centering of the plug in the casing. Thebottom or leading lip merges into the body portion of the plug to form aleading or nose portion. In the intermediate portion is a series,generally three, of wiping lips, and at the top or rear end of the plugis a sealing or cup lip, the inside of which is adapted to form aconical cup above the body portion of the plug.

The generally cylindrical metal portion of the plug used as a bottomcementing plug has a continuous bore, but the bottom of the conical cupprovides a diaphragm forming an obstruction at the upper end of thecylindrical reinforcing member. The generally cylindrical metal portionof the plug used as a top cementing plug has a closed rearward end, sothat there is a substantial thickness of cushioning and sealing rubberin the body of the plug between the top or closed end of the metal andthe cup portion of the plug.

Since the lips of the cementing plugs must necessarily be resilient inorder to seal inside the casing and so that the plugs may be pumpedthrough the casing, they do not provide adequate lateral support topreclude twisting of axial misalignment with the casing, either lateralor angular, or both, under the high pressures used in pumping. Thus withcementing plugs as commonly used, problems of leakage and contaminationof the cement slurry arise when the plugs become axially misaligned withthe casing as they are being pumped through it, or when they are seatedbecause the rubber or elastomeric material in the plugs tends to becomefluid under high pressure, or one side may tend to hang up or snag dueto different friction characteristics in the casing surface or at thejoints.

SUMMARY OF THE INVENTION In order to overcome the shortcomings of plugsof the prior art, therefore, it is one of the objects of this inventionto provide a cementing plug which is self-guiding and self-centering asit travels through the pipe.

Another object of the invention is to provide a cementing plug whichremains centered and axially aligned with the pipe through which it ispassing to assure uninterrupted wiping and sealing as it passestherethrough.

An additional object of the invention is to provide a cementing plug,the cup or sealing lip of which is increasingly backed up or supportedas pressure against the plug is increased, thus providing added strengthto the plug for more eifective sealing as needed when added pressure isapplied.

Still another object of the invention is to provide a cementing plugwith a positive pack-off and seal when seated to prevent any movement orflow of the cement during the setting period.

The invention is embodied in a plug of the type used for separatingfluids in a conduit, the plug having a generally cylindrical body havinga diameter less than the internal diameter of the conduit; a pluralityof circumferential flexible lips of elastomeric material carried by thebody coaxially therewith, axially spaced thereon and extending outwardlytherefrom, the lips having outer diameters greater than the internaldiameter of the conduit; the body and the lips defining a plug adaptedto be inserted in the conduit with the lips slidably engaging the innerwall of the conduit for resiliently centering the body in the conduitand for sealing the body to the inner wall to separate fluids in theconduit at opposite ends of the plug; wherein the improvement comprises:guide means carried by the body, the guide means extending radiallyoutward from the body and defining a generally cylindrical outer surfacecoaxial with the body, the surface having a diameter greater than thediameter of the body, less than the outer diameter of the lips, andsubstantially equal to the internal diameter of the conduit, the surfaceadapted, when the plug is in the conduit, to slidably contact the innerwall of the conduit for more positively centering the body in theconduit. Additionally, the improvement may comprise: the body having anelastomeric portion deformable in response to axially directed fluidforce acting on an end of the plug to expand the elastomeric portionradially; and a radial flange of elastomeric material integral with theelastomeric portion, the flange having a cylindrical outer surfacecoaxial with the body, the surface having a diameter greater than thediameter of the body, less than the outer diameter of the lips, andsubstantially equal to the internal diameter of the conduit; the surfaceadapted, when the plug is in the conduit, to slidably contact the innerwall of the conduit for more positively centering the body in theconduit and, in response to radial expansion of the elastomeric portion,to be expanded into packing relation with the inner wall of the conduit.

The problems encountered with plugs of the prior art as generally usedhave been alleviated with the plugs of the present invention byincorporation of the generally cylindrical guide or flange meansintegral With the plug body and extending outwardly to adjacent the boreof the casing. Without the guide means, because of the resilience of thelips and the clearance between the body of the plug and the casing, theplug is not positively centered in the casing and the sealing lip is notadequately backed up, so that, with a high differential pressure on thetwo sides of the plug, leakage may occur. This is particularlyundesirable when the plug is seated and supposed to pack off to precludeany leakage when the cement is being set or hardening. Plugs aspreviously made have not been able in many instances to prevent suchleakage, but the cylindrical guide ring or back-up ring of thisinvention overcomes that deficiency by centering the plug and backing upthe lip to prevent flow-by.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the accompanyingdrawings:

FIG. 1 is a longitudinal view, partly in section, of a top plug of theinvention;

FIG. 2 is a longitudinal View, partly in section, of a bottom plug ofthe invention;

FIG. 3a is a longitudinal sectional view of a well bore with a casingtherein, and the foregoing top plug and the foregoing bottom plug inplace inside the casing with cement slurry between the plugs;

FIG. 3b is a longitudinal sectional view similar to FIG. 3a, but withthe top plug having been pumped down against the bottom plug, and theslurry having passed through the ruptured diaphragm of the bottom plug;

FIG. 4 is a longitudinal view, partly in section, and on the same scaleas FIGS. 1 and 2, of the top plug inside the casing; and

FIG. 5 is a longitudinal view, partly in section, and on the same scaleas FIGS. 1 and 2, of the bottom plug inside the casing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the topcementing plug is shown with its elastomeric, generally cylindrical bodyportion 12, reinforced by being molded around a drillable metal insert14, which has a peripherally flanged forward or lower end 14' and isopen at its lower end to an inner bore 15. Molded integrally with thebody 12 is a series of spaced, outwardly and rearwardly extendingcircumferential elastomeric lips 16, 18, 20, including a nose lip 16,

merging into a conical nose 17 at the lower or leading end of the plug10, three wiping lips 18, and a sealing or cup lip 20, the inside ofwhich forms a cup 21 at the rearward or top end of the plug 10. Betweenthe bottom of the cup 21 and the closed or top end of the insert 14 is amass of elastomeric or rubber material forming a packer portion 13 ofthe body 12. Guide means in the form of a cylindrical peripheral gaugering 22 is provided between lips 18 and 20, the guide means 22 being inthe form of an integral, circumferential flange extension of theperiphery of the body 12 adjacent to and backed up by the packer portion13, and merging integrally with the rearward or following lip 20.

FIG. 2 shows the bottom cementing plug 30 with its elastomeric,generally cylindrical body portion 32, reinforced by being molded arounda generally cylindrical drillable metal insert sleeve 34, which has aninner bore and peripherally flanged ends 33, 33 at the rearward andforward ends, respectively. Molded integrally with the body 32 is aseries of spaced, outwardly and rearwardly extending circumferentialelastomeric lips 36, 38, 40, including a nose "lip 36, merging into aconical nose 37 at the lower or leading end of the plug 30, three wipinglips 38, and a sealing or cup lip 40, the inside of which forms a cup 41at the rearward or top end of the plug 30. Extending over the bottom ofthe cup 41 at the top of the body portion 32 is a frangible diaphragm44, which seals off the upper end of the opening 35 in the sleeve 34.Guide means in the form of a cylindrical peripheral gauge ring 42 isprovided between lips 38 and 40, the guide means 42 being in the form ofan integral, circumferential flange extension of the periphery of thebody 32, adjacent to and supported or backed up by the flange 33 of thereinforcing sleeve 34, and merging integrally with the rearward orfollowing lip 40.

As an example of typical plugs 10, 30 of this invention, for a typicalsize casing, with 5 /2 outside diameter and 4%" inside diameter, thedimensions of the plugs would be approximately as follows: overalllength 8%, with a body length 7%, outer body diameter 3%, and outerdiameter of the lips 5", diaphragm thickness and packer portion 13thickness 3". The cylindrical guide means 22, 42 should be 4 3/ indiameter for a close fit with the casing bore 57, and approximately 1"long, in the form of a flanged portion of the rearward end of the body12, 32 and merging into the sealing lip 20, The plugs 10, 30, exclusiveof the reinforcing inserts 14, 34, are molded of an abrasive-resistant,drillable elastomeric material, such as rubber or synthetic rubber ofShore A 45-65 hardness; and the inserts 14, 34, around which they aremolded, of a rigid, drillable material, such as cast aluminum.

In FIG. 3a is shown a well borehole drilled into an earth formation 52,with lengths of casing 56, joined by couplings 62, lowered into thedrilling mud 66 contained in the hole 50 until the guide shoe 58 on thebottom of the casing is adjacent to the bottom 51 of the hole 50, thecasing 56 being centered in the well 50 by means of centralizers 60, toform an annular space 54. Between the lengths of casing 56, at thecoupling 62, is an annular seat 64 on which rests the nose 37 of thebottom plug 30. Alternatively, seat 64 may be omitted, the nose 37 ofthe plug 30 resting on the top of guide shoe 58. Higher up inside thecasing is plug 10, with cement slurry 68 in the casing between the twoplugs 10, 30. In the casing 56 above the top plug 10 is pumping fluid ormud 67 for pumping down the top plug 10 and the cement slurry 68.

In FIG. 3b, the top plug 10 is shown having been forced downward by thepressured mud 67, its conical nose 17 engaging the cup 41 of the bottomplug 30, the differential pressure having first broken the frangiblediaphragm 44 of the bottom plug 30, allowing the cement slurry 68between the two plugs 10, 30 to flow downward through the opening 35 ofthe insert sleeve 34 of the bottom plug 30, the annular seat 64, thecasing 56, the guide shoe 58, and on out and upward into the annularspace 54 between the casing 56 and the hole 50, where the cement 68 canset and harden.

Referring to FIGS. 4 and 5, it is seen that when the cementing plugs 10,30' are in operating positions inside the casing 56, their resilientlips 16, 18, 20 and 36, 38, 40,

being larger than the inside bore 57 of the casing 56, preferably on theorder of /s to larger, are flexed inwardly in wiping and sealing contactwith the casing bore 57, while the guide means or cylindrical gaugerings 22, 42 are substantially in contact with the casing bore 57, thediametral clearance being preferably on the order of ,4, or a littlemore. It may be seen also that the body portions 12, 32 of the plugs 10,30 are of greater length than the diameter of the inner bore 57 of thecasing 56, in order to avoid any tendency of the plugs to tumble whenmoving through the casing. In FIGS. 4 and 5 also, it is evident that cuplips 20, 40 of plugs 10, 30 are prevented from extruding between thebody portions 12, 32 and the casing bore 57 When pressure is exertedagainst them because they are backed up by their respective cylindricalguide flange portions 22, 42.

In the use of the cementing plugs 10, 30 of this invention for cementinga string of casing 56 to a well bore 50, the latter containing drillingmud 66, the environmental conditions are generally as shown in FIG. 3aand as described aoove.

The forward or bottom cementing plug 30 is inserted in the casing 56 atthe top end (not shown) of the casing, a slurry valve (not shown) openedto allow cement slurry 68 under pressure behind the plug 30 to pump thelatter downward through the bore 57 of the casing 56 until the nose 37of the plug 30 seats on the annular seating ring 64, as shown in FIG.3a. When the plug 30 is inserted in the casing bore 57 and travelstherethrough, it assumes the configuration as shown in FIG. 5, the nose37 at the leading end being backed up by the lower flange 33 of theinsert sleeve 34 and the cylindrical guide means or flange 42 beingbacked up by the upper sleeve flange 33, thus assuring axial alignmentof the plug 30 with the casing 56. The lips 36, 38, 40 are in sealingcontact with the casing wall 57 to provide effective wiping and cleaningof the wall as the plug travels through it and effective sealing toprevent channeling or leakage of either drilling mud 66 or cement slurry68. This effective wiping and sealing is assured by the guide flange 42which is substantially in contact with the casing bore 57 to keep theplug 30 axially aligned with the casing 56 even when passing throughuneven spots in the casing bore 57 or when traveling past the casingjoints at each coupling 62. Without the lateral support provided by thereinforced guide means 42 closely guiding the plug 30 through the casingbore 57, the lips 36, 38, 40 by themselves, being flexible for sealingand wiping action, would be unable to resist the tendency of the plug totwist axially in the casing. Lip 40 of cup 41 is backed up by ring 42 aspressure is exerted against it, thus reinforcing the seal 40 andpreventing any extrusion of it, even at high pressures, around the bodyportion 32 of the plug 30.

When a suflicient, predetermined volume of cement slurry 68 has beenpumped into the casing 56 behind the bottom plug 30 for adequatelyfilling the annulus 54, the slurry valve (not shown) is closed, thefollowing or top cementing plug is inserted in the casing 56 at the topend (not shown) of the casing behind the cement slurry 68, and a pumpingfluid or mud valve (not shown) opened to allow fluid 67 under pressurebehind the plug 10 to pump the latter downward through the bore 57 ofthe casing 56 until the nose 17 of the plug 10 engages the cup 41 of theplug 30. Prior to the convergence of the two plugs 10, 30, however, theinitial pressure differential on either side of the diaphragm 44 of thebottom plug 30 has broken the diaphragm, allowing the cement slurry toflow downwardly through the ruptured diaphragm 44, the opening 35 of thereniforcing sleeve 34 of the plug 30, the annular seat 64, the casing 56below the plugs, the guide shoe 58, and on out and upward into theannular space 54 between the casing 56 and the well 50, where the cement68 may harden and set. See FIG. 3b. When the plug 10 is inserted in thecasing bore 57 and travels therethrough, it assumes the shape asilllustrated in FIG. 4, the nose 17 at the leading end being backed upby the flange 14' of the reinforcing insert 14 and the cylindrical guidemeans or flange 22 being backed up by the mass of elastomeric materialin the packer portion 13 of the top plug 10, thus assuring axialalignment of the plug 10 with the casing 56. The lips 16, 18, 20 are insealing contact with the casing wall 57 to provide effective wiping ofcement slurry 68 ahead of the plug and effective sealing to preventchanneling or leakage of either pumping fluid 67 or cement slurry 68.This effective wiping and scaling is assured by the guide flange 22,which is substantially in contact with the casing bore 57 to keep theplug 10 axially aligned with the casing 56 even when passing throughcasing joints at each coupling 62 or uneven spots in the casing bore 57.Without the lateral support provided by the reinforced guide means 22closely guiding the plug 10 through the casing bore 57, the lips 16, 18,20 by themselves, being flexible for sealing and wiping action, would beunable to resist the tendency of the plug to twist axially in thecasing. The guide means in the form of the flanges 22, 42 of the plugs10, 30, also assure their mutual alignment on convergence andcomplementary engagement of the nose 17 with the cup 41, providing apositive pressure against the latter to tightly force the lip 40 againstthe inner surface 57 of the casing 56. When thus engaged, as shown inFIG. 3b, pressure on the cup 21 from the fluid 67 tends to compress thepacker portion 13 of the top plug 10, forcing the cup lip 20 in tightengagement with the casing bore 57, the compression of the packerportion 13 at the same time forcing outwardly the peripheral guideflange 22 into tight packing engagement with the bore 57 of the casing56, and to back up the cup lip 20, thus precluding the further fluidflow which could adversely affect the setting of the cement 68.

After the cement 68 has hardened and set, and depending on subsequentoperations to be performed in the well, the residual cement, plugs 10,30, seat 64, and shoe 58 may be drilled out of the casing.

Above is described a typical cementing operation using a pair of plugs10, 30; however, a cement job may also be performed using only a bottomplug 30. The procedure is the same as described above to the point wherethe cement slurry 68 is pumped into the casing 56 behind the plug 30. Asuflicient, predetermined volume is used for adequately filling theannulus 54 with enough reserve so that the casing 56 still contains somecement 68 when the annulus 54 is filled. When the proper amount ofcement slurry 68 has been pumped into the casing 56, the slurry valve(not shown) is closed and the pumping fluid or mud valve (not shown) isopened to allow the fluid 67 under pressure behind the cement slurry 68to pump the latter downward through the bore 57 of the casing 56. Duringthe pumping, when the differential of pressure in the zone of thedrilling mud 66 to that in the zone of the cement slurry 68 is greatenough, the frangible diaphragm 44 ruptures, allowing the slurry 68 toflow downwardly through the ruptured diaphragm 44, the opening 35 of thereinforcing sleeve 34 of the plug 30, the annular seat 64, the casing 56below the plug 30, the guide shoe 58, and on out and upward into theannular space 54 between the casing 56 and the well 50. The cement 68may then harden and set, following which the residual cement, plug 30,seat 34, and shoe 58 may be drilled out of the casing, if desired.

It is evident that the plugs of this invention possess many novel andadvantageous features not found in plugs of the prior art. For example,the guide means 22, 42 provide positive centering and guiding of theplugs 10, 30 in the casing 56; and prevent misalignment or tumbling ofthe plugs, so that contact of the lips 16, 18, 36, 38, 40 is assured,resulting in more effective wiping and sealing against the casing bore'57. The guide rings or flanges 22, 42 are backed up positively by thepacker portion 13 and the insert flange 33, respectively, of the plugbodies 10, In the top plug 10, the packer portion 13 reacts underaxially applied pressure to become compressed longitudinally andexpanded radially, resulting in expansion of the guide means 22 intighter engagement with the inside 57 of the casing 56, for moreeffective centering and packing. Sealing of the lips 20, against thecasing bore 57 is also enhanced by their being backed up by the guidemeans 22, 42 substantially in contact with the inside of the casing.These advantages are not present in prior art plugs, in which the latterare only resiliently centered by the flexible lips, and in which, underhigh differential pressures, the sealing lip may be extruded into thespace between the plug body and the casing, resulting in leakage.

While two forms of the device have been illustrated and described, itshould be understood that various modifications will occur to thoseskilled in the art. For example, although the reinforcing inserts 14, 34have been described as being of drillable metal, other drillablematerials might be used, such as plastics or hard rubber; and althoughthe flanges or guide means 22, 42 are shown just below the cup lips 20,40 near the top of the elastomeric body portion '12, 32 of the plugs 10,30, respectively, or rearward from the direction of travel of the plugs,they could also be located nearer to the lower or leading ends of theplugs; and the rupturable diaphragm 44, rather than being of the sameelastomeric material as the body 32, could be of other frangiblematerials, such as plastics.

I claim:

1. A plug for separating fluids in a conduit, said plug having:

(a) a generally cylindrical body having a diameter less than theinternal diameter of the conduit;

(b) a plurality of circumferential flexible lips of elastomeric materialcarried by said body coaxially therewith, axially spaced thereon andextending outwardly therefrom, said lips having outer diameters greaterthan the internal diameter of the conduit;

(c) said body and said lips defining a plug adapted to be inserted inthe conduit with said lips slidably engaging the inner wall of theconduit for resiliently centering said body in the conduit and forsealing said body to said inner wall to separate fluids in the conduitat opposite ends of the plug; wherein the improvement comprises:

guide means carried by said body, said guide means extending radiallyoutward from said body and defining a generally cylindrical outersurface coaxial with said body, said surface having a diameter greaterthan the diameter of said body, less than the outer diameter of saidlips, and substantially equal to the internal diameter of the conduit,said surface adapted, when said plug is in the conduit, to slidablycontact the inner wall of the conduit for more positively centering saidbody in the conduit.

2. A plug as defined in claim 1 wherein said guide means comprises aperipheral flange portion of said body.

3. A plug as defined in claim 1 wherein said guide means is positionedadjacent to one end of said body.

4. A plug for separating fluids in a conduit, said plug having:

(a) a generally cylindrical body having a diameter less than theinternal diameter of the conduit;

(b) a plurality of circumferential flexible lips of elastomeric materialcarried by said body coaxially therewith, axially spaced thereon andextending outwardly therefrom, said lips having outer diameters greaterthan the internal diameter of the conduit;

(0) said body and said lips defining a plug adapted to be inserted inthe conduit with said lips slidably engaging the inner wall of theconduit for resiliently centering said body in the conduit and forsealing said body to said inner wall to separate fluids in the conduitat opposite ends of the plug;

wherein the improvement comprises:

(A) said body having an elastomeric portion deformable in response toaxially directed fluid force acting on an end of said plug to expandsaid elastomeric portion radially; and

(B) a radial flange of elastomeric material integral with saidelastomeric portion, said flange having a cylindrical outer surfacecoaxial with said body, said surface having a diameter greater than thediameter of said body, less than the outer diameter of said lips, andsubstantially equal to the internal diameter of the conduit;

(C) said surface adapted, when said plug is in the conduit, to slidablycontact the inner wall of the conduit for more positively centering saidbody in the conduit and, in response to radial expansion of saidelastomeric portion, to be expanded into packing relation with the innerwall of the conduit.

5. A plug as defined in claim 4 wherein said radial flange is positionedadjacent to one end of said body.

6. A plug for separating fluids in a conduit, said plug having:

(a) a generally cylindrical body having a diameter less than theinternal diameter of the conduit;

(b) a plurality of circumferential flexible lips of elastomeric materialcarried by said body coaxially therewith, axially spaced thereon andextending outwardly therefrom, said lips having outer diameters greaterthan the internal diameter of the conduit;

(0) said body and said lips defining a plug adapted to be inserted inthe conduit with said lips slidably engaging the inner wall of theconduit for resiliently centering said body in the conduit and forsealing said body to said inner wall to separate fluids in the conduitat opposite ends of the plug;

wherein the improvement comprises:

(A) said body having an elastomeric portion deformable in response toaxially directed fluid force acting on an end of said plug to expandsaid elastomeric portion radially; and

(B) a radial flange of elastomeric material integral with saidelastomeric portion, said flange having a cylindrical outer surfacecoaxial with said body, said surface having a diameter greater than thediameter of said body, less than the outer diameter of said lips, andsubstantially equal to the internal diameter of the conduit;

(C) a portion of said flange also being integral with a portion of oneof said lips for reinforcing the latter against axial displacement;

(D) said surface adapted, when said plug is in the conduit, to slidablycontact the inner wall of the conduit for more positively centering saidbody in the conduit and, in response to radial expansion of saidelastomeric portion, to be expanded into packing relation with the innerwall of the conduit.

7. A plug as defined in claim 6 wherein said radial flange is positionedadjacent to one end of said body. 8. A plug for separating fluids in aconduit, said plug having:

(a) a cylindrical body of elastomeric material having a diameter lessthan the internal diameter of the conduit and a length greater than theinternal diameter of the conduit, and having a forward end and arearward end; (b) a cylindrical reinforcing member of aluminum carriedby said body and having a forward end and a rearward end, said memberhaving an outwardly extending circumferential flange at either end, andan axial opening therethrough;

(c) a frangible diaphragm of elastomeric material, integral with saidbody at the rearward end thereof, and obstructing said opening at oneend of said member;

(d) a nose lip of elastomeric material, integral with said body, coaxialtherewith and extending outwardly and rearwardly therefrom adjacent itsforward end, with an outer diameter greater than the internal diameterof the conduit;

(e) a cup lip of elastomeric material, integral with said body, coaxialtherewith and extending outwardly and rearwardly therefrom adjacent toits rearward end, with an outer diameter greater than the internaldiameter of the conduit, the internal portion of said cup lip and therearward portion of said diaphragm defining a cup rearward of said dy;

(f) a plurality of wiping lips of elastomeric material, integral withsaid ody, coaxial therewith, extending outwardly and rearwardlytherefrom and axially spaced between said nose lip and said cup lip,with an outer diameter greater than the internal diameter of theconduit;

(g) a nose cone of elastomeric material, integral with said body,coaxial therewith and extending radially outwardly from said forwardflange of said reinforcing member, and merging conically with said noselip and said forward end of said body;

wherein the improvement comprises:

a flange portion of elastomeric material integral and coaxial with saidbody, extending radially outwardly from said rearward flange of saidreinforcing member, and merging with said cup lip, and with an outerperipheral surface having a diameter greater than the diameter of saidbody, less than the outer diameter of said lips, and substantially equalto the internal diameter of the conduit, whereby said flange is adaptedto reinforce said cup lip and to slidably contact the inner wall of theconduit for more positively centering said body when said plug is in theconduit.

9. A plug for separating fluids in a conduit, said plug having:

(a) a cylindrical body of elastomeric material having a diameter lessthan the internal diameter of the conduit and a length greater than theinternal diameter of the conduit, and having a forward end and arearward end;

(b) a generally cylindrical reinforcing member carried by said body andhaving a forward end and a rearward end, said member having an outwardlyextending circumferential flange at its forward end, and an axialopening at its forward end extending to a closure at its rearward end;

(c) a packer portion of elastomeric material, integral with said body,extending from the rearward end of said closure of said reinforcingmember to said rearward end of said body, and deformable in response toaxially directed fluid force acting on an end of said plug to expandsaid packer portion radially;

(d) a nose lip of elastomeric material, integral with said body, coaxialtherewith and extending outwardly and rearwardly therefrom adjacent toits forward end, with an outer diameter greater than the internaldiameter of the conduit;

(e) a cup lip of elastomeric material, integral with said body, coaxialtherewith and extending outwardly and rearwardly therefrom adjacent toits rearward end, with an outer diameter greater than the internaldiameter of the conduit, the internal portion of said cup lip and therearward end of said packer portion defining a cup rearward of saidbody;

(f) a plurality of wiping lips of elastomeric material, integral withsaid body, coaxial therewith, extending outwardly and rearwardlytherefrom and axially spaced between said nose lip and said cup lip,with an outer diameter greater than the internal diameter of theconduit;

(g) a nose cone of elastomeric material, integral with said body,coaxial therewith, and extending radially outwardly from saidcircumferential flange of said reinforcing member, and merging conicallywith said nose lip and said forward end of said body;

wherein the improvement comprises:

a flange portion of elastomeric material, integral and coaxial with saidbody, extending radially outwardly from said packer portion and mergingwith said cup lip, and with an outer peripheral surface having adiameter greater than the diameter of said body, less than the outerdiameter of said lips, and substantially equal to the internal diameterof the conduit, said surface adapted, when said plug is in the conduit,to slidably contact the inner wall of the conduit for more positivelycentering said body in the conduit and, in response to said radialexpansion of said packer portion, to be expanded into packing relationwith the inner wall of the conduit.

References Cited UNITED STATES PATENTS 2,124,710 7/1938 Pipes 166-1532,257,784 10/1941 Brown 166-153 3,100,534 8/1963 Herndon et al 166-1533,102,595 9/1963 Fisher et al. 166-156 3,191,678 6/1965 Hinson 166-153OTHER REFERENCES Composite Catalog of Oil Field Equipment and Services,1966-67 (27th revision), published by World Oil, Gulf PublishingCompany, Houston, Tex., (page 2281).

STEPHEN J. NOVOSAD, Primary Examiner.

